Re: [v4 2/4] arm64: kvm: add kvm cpu hotplug

Marc Zyngier
2015-05-26T13:29:13Z

On 08/05/15 02:18, AKASHI Takahiro wrote:
> This patch allows cpu cores to be up and down by adding
> kvm_arch_hardware_enable/isable(). This way, especially in kexec case,
> cores are reset to initial states and kexec can gracefully shutdown the
> system and reboot a new kernel from EL2.
>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> ---
> arch/arm/include/asm/kvm_host.h | 1 -
> arch/arm/kvm/arm.c | 29 +++++++++++++++++++----------
> arch/arm64/include/asm/kvm_host.h | 1 -
> 3 files changed, 19 insertions(+), 12 deletions(-)
>
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index 41008cd..ca97764 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -237,7 +237,6 @@ void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot);
>
> struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
>
> -static inline void kvm_arch_hardware_disable(void) {}
> static inline void kvm_arch_hardware_unsetup(void) {}
> static inline void kvm_arch_sync_events(struct kvm *kvm) {}
> static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index 251ab9e..e989925 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -87,11 +87,6 @@ struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void)
> return &kvm_arm_running_vcpu;
> }
>
> -int kvm_arch_hardware_enable(void)
> -{
> - return 0;
> -}
> -
> int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
> {
> return kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE;
> @@ -885,6 +880,9 @@ static void cpu_init_hyp_mode(void *dummy)

Since you removed the IPI, why do you keep the dummy argument?

> unsigned long stack_page;
> unsigned long vector_ptr;
>
> + if (__hyp_get_vectors() != hyp_default_vectors)
> + return;
> +
> /* Switch from the HYP stub to our own HYP init vector */
> __hyp_set_vectors(kvm_get_idmap_vector());
>
> @@ -921,6 +919,10 @@ static int hyp_init_cpu_notify(struct notifier_block *self,
> if (__hyp_get_vectors() == hyp_default_vectors)
> cpu_init_hyp_mode(NULL);
> break;
> + case CPU_DYING:
> + case CPU_DYING_FROZEN:
> + kvm_cpu_reset(NULL);
> + break;
> }
>
> return NOTIFY_OK;
> @@ -936,6 +938,7 @@ static int hyp_init_cpu_pm_notifier(struct notifier_block *self,
> void *v)
> {
> if (cmd == CPU_PM_EXIT &&
> + kvm_arm_get_running_vcpu() &&
> __hyp_get_vectors() == hyp_default_vectors) {
> cpu_init_hyp_mode(NULL);
> return NOTIFY_OK;
> @@ -1039,11 +1042,6 @@ static int init_hyp_mode(void)
> }
>
> /*
> - * Execute the init code on each CPU.
> - */
> - on_each_cpu(cpu_init_hyp_mode, NULL, 1);
> -
> - /*
> * Init HYP view of VGIC
> */
> err = kvm_vgic_hyp_init();
> @@ -1144,6 +1142,17 @@ out_err:
> return err;
> }
>
> +int kvm_arch_hardware_enable(void)
> +{
> + cpu_init_hyp_mode(NULL);
> + return 0;
> +}
> +
> +void kvm_arch_hardware_disable(void)
> +{
> + kvm_cpu_reset(NULL);
> +}
> +

Bahhh... Just rename cpu_init_hyp_mode to kvm_arch_hardware_enable, and
kvM_cpu_reset to kvm_arch_hardware_disable. I don't see the point of
keeping this indirection.

> /* NOP: Compiling as a module not supported */
> void kvm_arch_exit(void)
> {
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 6a8da9c..831e6a4 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -262,7 +262,6 @@ static inline void vgic_arch_setup(const struct vgic_params *vgic)
> }
> }
>
> -static inline void kvm_arch_hardware_disable(void) {}
> static inline void kvm_arch_hardware_unsetup(void) {}
> static inline void kvm_arch_sync_events(struct kvm *kvm) {}
> static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
>

--
Jazz is not dead. It just smells funny...